Study On Atmospheric Deposition Of Nitrogen And Phosphorus And Simulating Experiment Of Self-purification Of Water Body In Lake Taihu

Water Environmental Capacity?WEC?provides substantial information about how much nutrients can be discharged into the water body.So it is one of the key indexes for water environmental status and has been widely used for water management.Air depositions of nitrogen and phosphorus and self-purification capacity are the necessary parameters for the WEC calculation.In order to know the WEC of Lake Taihu,rain water samples were collected from Taihu Laboratory for Lake Ecosystem Research?TLLER?which is located at the east of Meiliang Bay and Dongshan Station which is located at the east of lake in January 2014 and December 2015.The air depositions of nitrogen and phosphorus and its seasonal variation at Lake Taihu were annlysized in this paper.In order to calculate the self-purification coefficients of N & P,self-purification experiments for Meiliang Bay and middle zone of the lake were conducted in April,July,November 2014 and January 2015.Analyse the trend of the process of self-purification experiment?144 h?and Meiliang bay?with mud,without mud?and the middle zone of lake Taihu through correlation analysis.The self-purification coefficients of four seasons in Meiliang bay?with mud,without mud?and the middle zone of lake taihu were obtained.The main conclusions are as follows:1.The amount of air depositions of nitrogen and phosphorus in sping and summer is significantly higher than that autumn and winter in lake Taihu.The amount of air deposition of nitrogen of 2014 and 2015 are 1,3230 t and 9,309 t respectively,as for the phosphorus of 2014 and 2015 are 750 t and 382 t.2.Conclude the result of the experiment of the self-purification of water body,the variation of dissolved oxygen?DO?: the change of DO in spring and summer is higher than that in autumn and winter.According to the initial values and final values of total nitrogen and total phosphorus and inorganic nitrogen of the water,it's found that the pollutants of water were degraded in four seasons and the trend of the degradation in spring and summer was more obvious than that in autumn and winter.The trends of the change of suspended solids?SS?and Chl-a are similar.3.Through the analysis of the water quality of the experiment,it can be seen that there is a strong correlation between total nitrogen,total phosphorus and SS.The correlation relationship among SS,DO and Chl-a were varied because of different reason,such as different season,water and area of the lake.The results are related to the concentration and activity of phytoplankton,temperature and light.4.The self-purification coefficients of N & P in Meiliang Bay?with mud,without mud?and the middle zone of lake Taihu were calculated.The self-purification coefficients of total nitrogen in four seasons of Meiliang Bay?without mud?were 0.0641 d^-1,0.1891 d^-1,0.1124 d^-1 and 0.0529 d^-1,the total phosphorus were 0.579 d^-1,0.249 d^-1,0.198 d^-1 and-0.192 d^-1;The self-purification coefficients of total nitrogen of Meiliang Bay?with mud?were 0.209 d^-1,0.126 d^-1 and 0.069 d^-1,the total phosphorus were 0.288 d^-1,0.226 d^-1 and-0.074 d^-1;The self-purification coefficients of total nitrogen of the middle zone of lake Taihu were 0.0286 d^-1,0.0813 d^-1,0.117 d^-1 and 0.0706 d^-1,the total phosphorus were 0.243 d^-1,0.034 d^-1,0.12 d^-1 and-0.0851 d^-1.It's found that the self-purification coefficients of N & P are different from others if they are in different area of lake or different seasons.The self-purification coefficients of N & P of many seasons are so small which can be ignored.